A. Field of the Invention
The present invention relates to lights utilizing an LED source. In particular, it relates to a lens adapted for use with the LED source to produce a predetermined output pattern in angle space. Optionally, it can additionally provide a retroreflective function for a variety of uses, including but not limited to, lighted markers or functional lighting for automotive vehicles and trailers.
B. Problems in the Art
Light emitting diodes (LEDs) have advantageous characteristics. They tend to be durable and shock resistant. They usually are long-lived. They also make efficient use of electrical power. They can be manufactured in small packages and thus present flexibility in design of light assemblies.
On the other hand, they are usually more expensive than other light sources such as incandescent sources. While incandescent sources tend to be substantially less robust, less power efficient and have shorter life expectancy, their development over the decades, and their inherent make up, allow them to be manufactured and sold for a very economical cost.
Still further, the amount of light output from individual LEDs is limited. While advances continue regarding lumen output for LEDs, there has been a hesitancy to move in the direction of using LEDs for lighting applications, particularly those involved with illumination, because of this limitation. This is particularly true in lighting applications where cost sensitivity is high.
One example is automotive lighting for semi-tractor trailers. Government regulations set forth minimum requirements for such things as side marker lights, clearance lights, and even brake and turn signal lights. A minimum amount of light energy is required at least in certain portions of the output distribution or beam of the light. Additionally, many of these lights must adhere to minimum intensity requirements in a predefined distribution pattern or geometric pattern. For example, an amber-colored side marker light for a semi-tractor trailer is required by DOT regulations or standards to have a minimum intensity at selected measurement points in a rectangular pattern. In other words, to meet the standards, the beam or output distribution of the light assembly must cover the rectangular pattern, and the intensity of the beam at the measurement points within the pattern must meet minimums. Such regulations for semi-tractor trailer amber side marker lights are publicly available.
Theoretically, the ways such a light could be designed to meet such requirements are almost unlimited. However, a practical semi-tractor trailer side light has certain design constrictions.
It has to be relatively small, compact, and thin in dimensions so that it can fit along the side of the trailer and not protrude very much out of the plane of the sidewall of the trailer or take up much space inwardly of that plane.
It must be economical. Some tractor trailers require a plurality of these lights. Since their function is to just provide visual marking of the physical side of the trailer, anything other than very low cost cannot be practically justified.
It must be relatively low power. It is powered by the truck's on-board electrical system. Sometimes the lights must be operated just on battery power.
It must be somewhat durable. It will be exposed to all sorts of environmental conditions and external forces.
The conventional state-of-the-art side marker is an incandescent source with a plastic, amber-colored, simple cover. Most incandescent sources emit a spherical or hemispherical ball of light (see cone in dashed lines in FIG. 1). Thus, an incandescent source with simple (non-optical) amber cover, would emit a diffuse ball of light. However, because incandescent sources are relatively inexpensive, to meet the minimum intensity requirements in a more constricted rectangular output pattern required by DOT regulations, higher intensity incandescent bulbs are used to basically blast light out to exceed minimums in the rectangle. However, a substantial amount of light falls outside the rectangle and therefore is essentially wasted relative to the minimums of the regulatory requirements. This is presently justified, however, again by the relatively low cost of relatively powerful incandescent sources. To keep the cost down, very simple, economical plastic covers are used. While more complex lenses or optical structures in the covers could be used with incandescent sources, they would be more costly and have been avoided in the art.
There have been attempts to move to LED sources for such lights. However, as mentioned, the limitations on intensity from such sources have resulted in those attempts using multiple LEDs to gain what is believed to be the needed intensity to meet the regulations. However, the cost of an LED source is the primary cost of such lights. Using plural LEDs makes them substantially more expensive and hard to justify for such applications even though they would be likely more robust, last longer in operating life, and not be substantially different than incandescent sources in power efficiency.
Another factor has come into play regarding these types of lights. Owners/operators of semi-tractor trailer combinations like to have certain aesthetic appearance for their lights. For example, some owners like a round-shaped light fixture. Others like rectangular. This is not much of an issue for incandescent sources which have a simple plastic cover and “blast” light out in a spherical or circular pattern. The simple lens can easily molded to different shapes. However, if any optics or lensing is used to try to control the light, it makes it difficult to design.
Still further, because some of these lights are recessed, the ability to retrofit the fixture or assembly into existing mounting structure on the tractor trailers would usually be advantageous. This would be a valuable consideration.
Still further, some regulations require both illumination and retroreflectance functions for certain vehicles. It would be desirable to be able to satisfy some of these multiple requirements with one lighting fixture.
Other semi-tractor trailer lighting applications have similar issues or concerns as side marker lights. Still further, other automotive lighting applications, for example, for other types of automobiles, including but not limited to cars, other types of trucks, and other types of trailers, have similar issues. And, other lighting applications outside of automotive applications have analogous issues.
It has therefore been identified that there is a real need in the art for improvement in this area.